The president's courageous decision to deploy a major military force in Saudi Arabia has raised not only the prospects of success but also the stakes of defeat. The United States has in fact passed the point of no return.

It therefore becomes crucial to assess how success and failure are to be defined. The U.N. Security Council has unanimously demanded the unconditional withdrawal of Iraqi forces and the restoration of the legitimate government. The United States has justified its interdiction of the sea lanes as a response to a request of the exiled Kuwaiti government.

In these circumstances, should Iraq manage to remain in Kuwait or exercise indirect control through some puppet, the American show of force will turn into a debacle. If in the end Iraq controls Kuwait and U.S. forces stay in Saudi Arabia, the crisis will have ended in a demonstration of the irrelevance of America and of world opinion. In any event, neither Arab nor American politics would long sustain significant troop deployments in Saudi Arabia. The argument that we have saved Saudi Arabia will be overwhelmed by the perception of an American failure that would shake political, economic and financial stability everywhere. Indeed, even attainment of the U.N. objectives might provide only a breathing space if Saddam Hussein remains in office and Iraq continues to build up its nuclear and chemical weapons potential.

Time is not on our side. American staying power in the face of public, regional and allied pressures is usually inversely proportional to the scale of our deployment. Thus, if after a certain interval the conflict appears to settle down to a siege, the United States will be obliged to consider new measures to bring it to a conclusion.

Success for Iraq in Kuwait would usher in a series of upheavals certain to culminate in a general Middle East war. A government as cautious and as dedicated to anonymity as Saudi Arabia's would never have asked for the assistance of foreign troops had it not considered the very survival of the state at stake. Nor would the Arab summit have condemned a brother country. Nor would Egypt, Syria and Morocco have sent troops to assist Saudi Arabia. Likewise, in the developing world, where so many countries have more precarious and even more recent frontiers as well as covetous neighbors, a victory by Iraq could inaugurate a time of troubles.

The vital interests of the industrial states are affected most directly. If Iraq succeeds in making the annexation of Kuwait stick, it could determine the price of oil by blackmailing the states of the Arabian peninsula -- which together with Kuwait and Iraq control some 40 percent of the world's oil reserves -- into reducing their oil production.

The United States had three choices in dealing with the crisis: it could passively endorse whatever consensus emerged in the United Nations; it could support whatever the industrial democracies -- all of which are more dependent on Mideast oil than the United States is -- were prepared to do in concert; or it could take the lead in opposing Saddam Hussein and try to organize international support for an effort in which the United States would bear the principal burden.

There were ample excuses for avoiding a decision. The most fashionable is the argument that the defense of the area should be an Arab matter. But in the end, alibis cannot change the consequences of failure to resist. None of the Arab states is strong enough even in combination to defeat the Iraqi army, toughened in a 10-year war, supplied with advanced military technology during that time by the Soviet Union and France and buttressed by economic assistance from the other industrial democracies, including the United States. Such an argument marks the reemergence of American isolationism, especially among the conservatives. Allowed to prevail, it would conclude with America's abdication at the very moment when the old East-West conflict has been won.

Another argument to avoid a U.S. role is that even if Iraq controlled all the oil in the Gulf, it would still have to sell it in a world market governed by the laws of supply and demand. But were Iraq to achieve its strategic design, it would be able to determine the level of supply by taking production away from sparsely populated principalities in the Arabian peninsula without hurting its own population. The ability to cause a worldwide economic crisis is not the sort of power to be left in the hands of a ruler who has attacked two of his six neighbors, is engaged in mortal conflict with two others and has used poison gas against his own dissident population.

The administration must have concluded that anything other than a leadership role for the United States would have ended with making Iraqi domination of Kuwait permanent and led to the collapse of the moderate governments in the region including Egypt. Having committed the United States to a leadership role, President Bush made another crucial decision. The American military role could have been confined to interdiction at sea and a token force on the ground to make clear that an attack on Saudi oil fields would lead to war with the United States. President Bush and his advisers opted for a massive deployment. They seem to have reasoned that the U.N.'s unexpected sanction might change Saddam Hussein's calculation. He may well not have originally intended to seize the Saudi oil fields. Had there been no meaningful resistance, he would not have needed to do so. The rulers of the Arabian peninsula -- in Saudi Arabia as well as in the Emirates -- would have yielded to Iraqi pressures or been overthrown, more likely both.

But once the sanctions were voted, Saddam Hussein's calculus was bound to change. So long as oil prices remain steady, the sanctions are likely to be sustained for many months. And prices will remain at more or less present levels if Saudi Arabia increases its production by 2.5 million barrels. The remaining 1.6 million barrels of the 4.1 million barrel present shortfall caused by the loss of oil from Iraq and Kuwait, can be pieced together (at least until the winter) from Venezuela, the Emirates, Nigeria and other small producers. But if Saudi production can be destroyed or even severely reduced, the absence of Iraqi and Kuwaiti oil will lead to an explosive rise in oil prices. With Saudi production crippled and a worldwide depression looming, it would become increasingly difficult to maintain sanctions; Saddam Hussein would win the endurance contest.

President Bush and his advisers must have concluded that once they committed military forces, the best hope of ending the crisis quickly was to assemble an overwhelming force to overawe such a threat and to be able to go further if necessary, but the administration needs to calculate very carefully the window of opportunity it has available to achieve its objectives.

The administration must take care not to wallow in the wide domestic and international support it now enjoys. For the perfectly legitimate concern about the probability of success expressed by talk show hosts and newspaper columnists coupled with insistent reassurances by administration spokesmen will over time weaken the credibility of the American enterprise. The longer it lasts, the more American governmental procedures and Congressional inquiries will take their toll. At some point the familiar question of the light at the end of the tunnel is bound to surface.

The situation within the Middle East is also likely to grow more precarious the longer the crisis festers. The impact on the Arab world of anti-Western propaganda from Baghdad and the skillful linking of the issues of Kuwait and of Palestine must not be underestimated. A coup in one of the emirates or sabotage in the oil fields would send another shock through the region and the world economy.

The time required for the sanctions to work must be balanced against the factors undermining international cohesion. Such an analysis must keep in mind that the acid test of the sanctions will be not how much oil is prevented from leaving the region but how few supplies are allowed to enter Iraq. Iraqi oil exports are relatively easily blocked. But Iraq's frontiers are long, and less bulky goods such as food can seep in. And the likelihood of this happening will grow the longer the crisis lasts and the more Iraq's neighbors conclude that they may have to live with the Iraqi dictator, however dangerous he may be.

A sharp and short crisis is far more in the interest of all concerned with moderation than a long siege. I am not in a position to know whether sanctions can work within the time constraints outlined here. I also realize that the United States must consider the risk that a more aggressive course might take away some of the current international support. At the same time, that support would not survive the appearance of an American defeat. The United States stands to lose the most from a long siege -- whatever the relative immediate economic impact on Europe and Japan. An ignominious withdrawal following the debacle in Lebanon -- and any withdrawal however dressed up without achieving our objectives would be ignominious -- would end America's stabilizing role in the Middle East. And no other country could take its place. It would gravely weaken the Bush administration's capacity to overcome the economic crisis that would inevitably follow.

It would be a mistake to focus only on America's difficulties. In the end, Iraq is a heavily indebted developing country with a population of only 16 million that has just ended a debilitating 10-year war with Iran, and which has hostile relations with four of its six neighbors. It is in no position to enter into a protracted conflict with the United States. Saddam Hussein proved during the Iran war that he is prepared to negotiate when necessary. His most recent offer agreed to the principle of withdrawal from Kuwait, albeit under outrageous conditions. It may be the beginning of an attempt at negotiation obscured by bluster once the reality of the stark choices before Iraq sinks in. Then the offer to withdraw may reemerge stripped of its absurd baggage.

But the United States cannot afford to be diddled, and it simply cannot afford to lose. If it should be concluded that sanctions are too uncertain and diplomacy unavailing, the United States will need to consider a surgical and progressive destruction of Iraq's military assets -- especially since an outcome that leaves Saddam Hussein in place and his military machine unimpaired might turn out to be only an interlude between aggressions.

It would be irresponsible for an outsider to press for a course of action in a situation so dependent on information not available to the kibitzer. But it is important to understand that America has crossed its Rubicon. All those concerned with global peace and world economic well being should subordinate whatever tactical misgivings they may have to standing behind the only policy that can now succeed.